The present invention is generally in the field of reinforced window systems and more specifically it is related with window systems which offer improved protection against blast and impact hazards.
The terms blast window and blast resistant refer to the ability of a window system to withstand blast caused for example by an explosion of a bomb, significantly strong wind, etc. A reinforced window may also be a window pane to which a film of material is adhered, as known per se. The terms impact window and impact resistant refer to the ability of withstanding impact force applied for example by kinetic energy of arms or shrapnel, force applied by vandalism actions, etc.
The ever-growing threat of what was in the past referred to as non conventional war, namely chemical and biological war, has led to some recent requirements to provide blast-resistant and gas-tight window systems. In addition, it is often a requirement that such window systems also have improved resistance to impact hazards, such as, for example, resistance to bullets fired from firearms, shrapnel of explosive charges and bombs, and even vandalism, e.g. attempts to break into a building or crowds trying to brake through.
A variety of windows offer blast resistance and impact resistance solutions, most of which typically offer a single type of protection, namely blast resistant or impact resistant. Other window systems offer dual protection but do not provide the climatic benefits of double glazing window systems. One considerable disadvantage of known window systems is that a single, reinforced impact-resistant laminated window absorbs also some of the blast energy (owing to its relative rigidity) and in many cases may forcefully fly into a room causing severe damage and casualties.
Furthermore, for fixing a reinforced laminated window of the aforementioned type within an opening in a wall, a suitable structure and reinforcement of the opening are required, which at times are not feasible for retrofit.
U.S. Pat. No. 3,624,238 is concerned with a bullet resistant structure of laminated character comprising outer faces or piles of safety glass with an intermediary ply formed of a polycarbonate a resin.
U.S. Pat. No. 4,312,903 deals with an impact resistant double glazed structure and is concerned in particular with the thickness of the layers of the laminated window panes, and their chemical compositions.
U.S. Pat. No. 5,059,467 is concerned with a protective ballistic panel including a first-impact, front layer and a second rear layer. The layers being spaced from one another by a semi-elastic material, defining a sealed space. However, the panel is for use as a personnel protective shield and is not concerned at all with providing blast resistant protection or with serving as a window system.
U.S. Pat. No. 4,625,659 discloses a bullet and explosion proof window or door system comprising two spaced apart panels whereby the outer panel is spaced from a support soffit such that a gap is formed for providing a ventilation channel. However, peripheral portions of the panels are fitted with a security layer in order to prevent projectiles from entering through the ventilation gap.
Double glazing windows typically comprise an outer window pane and an inner window pane spaced apart from the first window pane, with a sealed space between the window panes. The sealed space typically holds dries air or other gas and serves for improving thermal isolation of the construction in which the window is installed. The gas is dried so as to eliminate condensation within the sealed space.
Such double glazing windows may be fixed window systems (wherein the framework is fixed within an opening in a wall and the window is not capable of being opened), casement window systems (swingably or tiltably opened), or sliding window systems.
It is an object of the present invention to provide a window system offering improved resistance whilst not interfering with its function as a window, namely, providing good visibility therethrough. By one specific embodiment, the window system is a double-glazing type, whereby it provides also good climatic and acoustic isolation between an in-side and an out-side thereof.
According to the present invention, there is provided a reinforced window system for mounting within an opening in a wall, the window system comprising a first frame corresponding with an out-side of the wall and a second at least partial frame fixed behind said first frame and corresponding with an in-side of the wall; at least the first frame supports a reinforced window pane; said first frame bears against said second at least partial frame such that forces applied to the first fame in a direction normal to the pane are at least partially absorbed and dampened by the second at least partial frame.
The term at least partial frame as used herein the specification and claims as referred to the second frame denotes one or more profiled members extending behind (inward) of said first frame, which second frame may be a complete, closed frame corresponding in shape with that of the opening in the wall, or may be one or more profiled members connected or disconnected from one another.
Typically, the first frame and the second at least partial frame are independently fixed to the wall. Alternatively, the second at least partial frame is fixed to the first frame. By one particular embodiment said first frame bears against said second at least partial frame such that forces applied to the first fame are at least partially transferred to the second at least partial frame. By a different embodiment, there is a gap between the first frame and the second at least partial frame, with or without a gasket member therebetween.
Still typically, the first frame is larger than the second at least partial frame and accordingly, where the second at least partial frame also supports a window pane, the second window pane is smaller than the first window pane.
Preferably, at least a peripheral portion of the first frame is concealed by an overlapping protective portion either integrally formed with the wall or applied over the wall, for protection of the first frame.
According to an embodiment of the present invention there is provided a blast and impact resistant double glazing window system comprising a front laminated window facing the direction of impact and a rear laminated window opposite the direction of impact, said front and rear laminated windows being spaced apart from one another by a hermetically sealed space; each of the front laminated window and the rear laminated window being one of an impact resistant window and a blast resistant window; the front laminated window is fixed to a first frame fixable within an opening of a wall, and the rear laminated window is fixed to a second at least partial frame fixable within the wall""s opening.
By a most preferred embodiment, the front laminated window is impact resistant and the second laminated window is blast resistant. The terms impact resistant and blast resistant define the mechanical properties of the laminated window to withstand impact and blast threats, respectively, as known per se.
Preferably, the sealed space between the laminated windows is filled with a dried gas, such as, for example, dries air. This arrangement improves climatic and acoustic isolation and prevents condensation of liquid vapor within the sealed space.
According to a preferred embodiment, either or both the first frame and the second at least partial frame are fixed to the wall in a gas-tight manner so as to prevent noxious gases from entering the room.
According to still a preferred embodiment, wherein the front laminated window is larger than the rear laminated window. Alternatively, the front laminated window is smaller than the rear laminated window.
Typically, the front laminated window has an outer face corresponding with an exterior side of the wall, and the rear laminated window has an inner face corresponding with an interior side of the wall; the first frame is in-accessible from the exterior side. According to one particular such design, at least a peripheral portion of the outer face of the front laminated window is concealed by an overlapping portion of the wall.
The first frame and the second at least partial frame may be fixed to one another, with one or both of the first frame and the second at least partial fame being fixed to the wall or, alternatively, each of the first frame and the second at least partial frame are independently fixed to the wall.